JPH05173115A - Liquid crystal element - Google Patents

Abstract

PURPOSE:To provide the useful liquid crystal element which has a liquid crystal layer formed by dispersing a liquid crystal material in resin and also has high visibility and a wide utilization range. CONSTITUTION:The reflection type liquid crystal element 1 is equipped with the liquid crystal layer 2 formed by dispersing the liquid crystal material 2b in the resin 2a and light which is made incident on the top surface side of the liquid crystal layer 2 is reflected by a reflecting surface R provided on the reverse surface side of the liquid crystal layer 2 to return to the top surface side. The reflecting surface R is colored and pigment is added to the liquid crystal material to absorb light having wavelength corresponding to the color of the reflecting surface when the liquid crystal layer 2 is opaque.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflective liquid crystal device having a liquid crystal layer in which a liquid crystal substance is dispersed in resin.

[0002]

2. Description of the Related Art As a liquid crystal element expected to be useful,
There is a liquid crystal element including a liquid crystal layer (polymer dispersed liquid crystal composite film) 51 in which a liquid crystal substance is dispersed in a (polymer) resin. As shown in FIG. 10, the liquid crystal material 51 is contained in the resin 51a.
Liquid crystal layer 5 in which b is dispersed in the form of droplets (about 0.5 to 3 μm)
1 and the liquid crystal layer 51 is sandwiched between transparent electrodes 54 and 55 formed on transparent substrates 52 and 53, which is a transmissive element. Reference numeral 57 is a filter.

Whether or not a voltage is applied to the electrodes 54 and 55 causes a change in visibility, transparent or opaque, to appear. However, high visibility cannot be expected and practicality is poor only by the change from transparent to opaque. On the other hand, in the case of a liquid crystal element, normally, the light incident from the front surface side of the liquid crystal layer is reflected by the reflection surface provided on the back surface side of the liquid crystal layer and returns to the front surface side. And highly practical.

[0004]

In view of the above circumstances, an object of the present invention is to improve the visibility of a reflective element having a liquid crystal layer in which a liquid crystal substance is dispersed in a resin.

[0005]

In order to solve the above-mentioned problems, the present invention comprises a liquid crystal layer in which a liquid crystal substance is dispersed in a resin, and the light incident from the front surface side of the liquid crystal layer is the back surface of the liquid crystal layer. In a reflective liquid crystal element that is reflected by a reflective surface provided on the side and returns to the surface side, the reflective surface is colored, and a dye is added to the liquid crystal substance, When the layer is opaque, light having a wavelength corresponding to the color of the reflecting surface is absorbed.

Hereinafter, the liquid crystal element of the present invention will be specifically described with reference to FIG. As shown in FIG. 1, the liquid crystal element 1 of the present invention is provided with electrodes 3 and 4 on both sides of a liquid crystal layer 2 so that a voltage can be applied to the liquid crystal layer 2 and the liquid crystal layer 2 has a surface side. The incident light is reflected by a colored reflecting surface R provided on the back surface side of the liquid crystal layer 2 and returns to the front surface side.

The liquid crystal layer 2 is a so-called PDLC type liquid crystal layer in which the liquid crystal substance 2b is dispersed in the resin 2a in the form of droplets. The resin 2a used here is a thermosetting resin,
Examples include thermoplastic resins and photocurable resins. The liquid crystal substance 2b is preferably one having a large difference in refractive index in liquid crystal molecules and positive dielectric anisotropy, and examples thereof include nematic liquid crystals and cholesteric liquid crystals.

The electrode 3 on the light incident side is a transparent conductive film (ITO).
A film, a NES film or the like) formed on the surface of the transparent substrate (glass plate or polyethylene terephthalate film) 7 is used. The colored reflective surface (colored reflective surface) R on the back surface side of the liquid crystal layer 2 is provided by forming the colorant layer 5 on the electrode 4. As the electrode 4, a transparent conductive film (ITO film, NESA film, etc.) or a metal conductor film (copper, aluminum, gold, etc.) formed on the surface of the support substrate 8 is used.

In the liquid crystal element 1 of the present invention, a dye is added to the liquid crystal substance 2b of the liquid crystal layer 2. When no voltage is applied, the liquid crystal substance 2b becomes in a random state and the liquid crystal layer 2
Becomes opaque, but at this time, the dye also follows the liquid crystal substance 2b and becomes in a random state, and absorbs light having a wavelength corresponding to the color of the reflecting surface (the liquid crystal layer 2 becomes the color of the dye). .. On the other hand, when a voltage is applied, the liquid crystal substance 2b is in an alignment state, and at this time, the dye also follows the liquid crystal substance 2b and is in an alignment state, so that the liquid crystal layer 2 becomes transparent and light of a wavelength corresponding to the color of the reflecting surface is emitted. Make it transparent. As described above, the dye is changed according to the alignment state of the liquid crystal substance, and the dichroic dye that causes the liquid crystal layer 2 to change from substantially colorless to colored is used.

At this time, if the color of the reflecting surface and the color of the pigment are selected so as to have a complementary color relationship, the visibility is greatly improved. When no voltage is applied, the dye in the liquid crystal substance 2b absorbs the light of the wavelength of the color of the colored reflection surface R, and the colorant layer 5 on the colored reflection face R absorbs the light of the wavelength of the dye color in the liquid crystal substance 2b. As a result, the surface (visible surface) of the liquid crystal element 1 becomes almost black. When a voltage is applied, the dye in the liquid crystal substance 2b does not absorb the light of the wavelength of the color of the colored reflective surface R, is reflected by the colored reflective surface R and returns to the surface side, so that the colored reflective surface R emerges. The visibility is enhanced by the cooperative action of the color of the dye in the liquid crystal substance 2b and the color of the colored reflecting surface R. In this case, the dye in the liquid crystal substance 2b may be a single-component dichroic dye. When multiple dichroic dyes must be mixed, there is often no suitable combination that meets the required conditions such as absorbance and dichroic ratio, solubility in liquid crystal substances, weather resistance, etc. Therefore, the effect that one-component dichroic dye is sufficient is great.

It should be noted that if a non-reflective coating layer 9 is provided on the incident side in order to cut off light of the wavelength of the color of the dye in the liquid crystal substance when no voltage is applied, the visible surface looks blacker when no voltage is applied. It is preferable because the visibility becomes higher. Examples of the material for forming the antireflection coating layer 9 include MgF _{2 and the} like. Such a liquid crystal element having high visibility is highly suitable as a display element. As shown in FIGS. 2 and 3, the electrode 4 on the back surface side of the liquid crystal layer 2 is suitable for a display element including a group of pixel electrodes 4a ... Arranged in a two-dimensional matrix. When the voltage is applied, the color of the colored reflective surface R is directly above the pixel electrode 4, and the voltage is not applied between the pixel electrodes 4 and the color is substantially black so that the visibility is high. In the case of the liquid crystal element 1 of FIG. 2, the pixel electrode 4a is drawn to the back side by the through-hole conductive path 4b penetrating the support substrate 8, and the signal wiring is formed on the back side without being formed on the same side as the pixel electrode 4a. Therefore, it is possible to improve the pixel density by narrowing the interval L.

The liquid crystal element of the present invention is not limited to the above structure. Instead of the configuration in which the colored reflecting surface R is on the surface of the electrode 4, both the electrode 4 and the supporting substrate 8 are transparent, and a substrate having the colored reflecting surface R may be provided on the back side of the supporting substrate 8. INDUSTRIAL APPLICABILITY The liquid crystal element of the present invention can be used for conference displays, sign displays, advertising media and the like.

[0013]

The change in the visible state on the surface of the liquid crystal element of the present invention is exemplified by the case where the dye in the resin is blue and the colored reflecting surface is colored yellow by forming a yellow dye layer on the electrode surface. To explain. First, the visual recognition state when no voltage is applied to the electrodes will be described.

As shown in FIG. 4, visible light (white light) having a wavelength of 380 to 780 nm enters from the surface side of the liquid crystal element. When no voltage is applied, the liquid crystal layer is opaque and has the color of the dye in the liquid crystal substance, and the dye absorbs green and red light having wavelengths corresponding to the yellow color, and as shown in FIG.
Only blue light hits the colored reflective surface. Since the yellow dye generally absorbs blue light, there is no light returning to the incident side as a result, and as a result, the visible surface becomes substantially black.

Next, the visual recognition state when voltage is applied to the electrodes will be described. Again, as shown in FIG. 7, visible light (white light) having a wavelength of 380 to 780 nm enters from the surface side of the liquid crystal element. When a voltage is applied, the liquid crystal layer is transparent, and light of all colors hits the colored reflection surface, as shown in FIG. The blue light is absorbed by the yellow pigment, but as shown in FIG. 9, the green and red lights having the wavelengths corresponding to the yellow color are reflected and returned to the incident side. The surface becomes yellow.

[0016]

Embodiments of the present invention will be described below. -Example 1-A blue dye (M137 manufactured by Mitsui Toatsu Dyes Co., Ltd.) was used as a dichroic dye added to the liquid crystal substance. The colored reflection surface was provided by forming a colorant layer of a yellow dye (Benzidine Yellow GR manufactured by Tokyo Ink Co., Ltd.) on the electrode surface.

The visible state when no voltage was applied to the electrode was black, and the visible state when a voltage was applied to the electrode was yellow. -Example 2-A red dye (M86 manufactured by Mitsui Toatsu Dyes Co., Ltd.) was used as a dichroic dye added to the liquid crystal substance. The colored reflective surface was provided by forming a colorant layer of bluish green dye (Fast Green Lake D, manufactured by Daito Kasei Co., Ltd.) on the electrode surface.

The visible state when no voltage was applied to the electrode was black, and the visible state when a voltage was applied to the electrode was bluish green. For comparison, when an element in Example 2 which did not form a bluish green dye on the electrode surface was examined in the same manner, the visually-recognized state when a voltage was applied was mere colorless. -Example 3-A bluish green pigment (SI-484 manufactured by Mitsui Toatsu Dyes Co., Ltd.) was used as a dichroic pigment added to the liquid crystal substance. The colored reflection surface was provided by forming a colorant layer of red dye (Symuler Red 3014, manufactured by Dainippon Ink and Chemicals, Inc.) on the electrode surface.

The visible state when no voltage was applied to the electrode was black, and the visible state when a voltage was applied to the electrode was red.

[0020]

As described above, in the liquid crystal element of the present invention, the reflecting surface for reflecting the incident light is colored, and the liquid crystal substance is added with a dye so that the liquid crystal layer is opaque. Since the light of the wavelength corresponding to the color of the reflecting surface is sometimes absorbed, the liquid crystal element has a high visibility and a wide range of use and is useful.

When the color of the reflecting surface and the color of the pigment are in a complementary color relationship, in addition, even in the case of a single-component pigment, the visible surface is changed to black and the color of the reflecting surface to greatly enhance the visibility. There is an advantage that can be done.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration example of a liquid crystal element of the present invention.

FIG. 2 is a cross-sectional view showing another configuration example of the liquid crystal element of the present invention.

3 is a plan view showing a pixel electrode of the liquid crystal element of FIG.

FIG. 4 is a graph showing a relationship between wavelength and intensity of light incident on a liquid crystal element.

FIG. 5 is a graph showing the relationship between the wavelength and the intensity of light that hits the reflecting surface.

FIG. 6 is a graph showing a relationship between wavelength and intensity of light returning to the incident side.

FIG. 7 is a graph showing the relationship between wavelength and intensity of light incident on a liquid crystal element.

FIG. 8 is a graph showing the relationship between the wavelength and the intensity of light that hits the reflecting surface.

FIG. 9 is a graph showing a relationship between wavelength and intensity of light returning to the incident side.

FIG. 10 is a cross-sectional view showing a configuration of a conventional liquid crystal element.

[Explanation of symbols]

 1 Liquid crystal element 2 Liquid crystal layer 2a Resin 2b Liquid crystal substance 3 Electrode 4 Electrode R Colored reflective surface

Front page continuation (72) Inventor Eiji Shiohama 1048, Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Works Co., Ltd.

Claims (5)

[Claims] 1. A liquid crystal layer in which a liquid crystal substance is dispersed in a resin is provided, and light incident from the front side of the liquid crystal layer is reflected by a reflecting surface provided on the back side of the liquid crystal layer and returns to the front side. In such a reflective liquid crystal element, the reflecting surface is colored, and a dye is added to the liquid crystal substance, and light having a wavelength corresponding to the color of the reflecting surface when the liquid crystal layer is opaque. A liquid crystal element characterized by being absorbed. 2. The liquid crystal element according to claim 1, wherein the color of the reflecting surface and the color of the dye in the liquid crystal substance have a complementary color relationship. 3. The liquid crystal element according to claim 1, wherein the electrode surface on the back surface side of the liquid crystal layer is a reflective surface, and the reflective surface is colored by a colorant layer formed on the electrode surface. .. 4. The dye is a dichroic dye whose alignment state changes in accordance with the change of the alignment state of the liquid crystal substance.
The liquid crystal device according to any one of 1 to 3 above. 5. The color of the reflective surface is visually recognized on the liquid crystal surface when a voltage is applied to the liquid crystal layer, and the black color is visually recognized on the liquid crystal surface when a voltage is applied to the liquid crystal layer. The liquid crystal device according to any one of 1 to 3 above.